1. Field of the Invention
The present invention relates to an information storage system, information transfer system and to a storage medium utilized in those systems for distributing information on a semiconductor storage medium, and relates in particular to a method for preventing illegal copying while storing information of high added value onto general information storage mediums such as large capacity magnetic storage in personal computers not having a function to prevent copying of information, and to a method for transferring the same information between storage mediums without copying.
1. Description of Related Art
One method of the related art for distributing information with high added value while preventing illegal copying is a system disclosed in unexamined Japanese Patent publication No. 2000-90039. A brief explanation of the operation of the device is given while referring to FIG. 9.
A block diagram showing a system for preventing unauthorized use by copying is shown in FIG. 9. In the system in FIG. 9, a music server 903 and a client 902 are connected by an Internet 901. A public key and a secret key are made based on the characteristic ID of the playback equipment 911, by the client 902. The public key is sent from a personal computer 910 to a server 903 and registered (stored). The secret key is retained in a playback equipment 911. The client 902 makes a request to the server 903 for distribution of the music data. Encryption with the registered public key is performed for music data extracted from a music data base 922. The encrypted music data is sent to the client 902 and stored in the playback equipment 911. During play, the music data is decrypted with the secret key held in the playback equipment 911 while being played. The music data stored in the playback equipment 911 was encrypted with a key made based on the unique ID of the playback equipment 911 and therefore cannot be played back on other playback equipment.
Another method for transferring information with high added value is disclosed in unexamined Japanese Patent publication No. H11-259964. The operation of the device is briefly described while referring to FIG. 10.
A flowchart of the information transfer system of the related art is shown in FIG. 10. In this device, when data is copied by transfer to the transfer destination, the playing back of the transfer source data is prohibited. A unique identifier is set beforehand into the device at the transfer destination. In step 1050, when the transfer source device is connected to the transfer destination device, an identifier is sent from transfer destination device in step 1051. In step 1052, a search is made in the (pre-registered) identifier control table for the identifier that was sent, and in step 1053 whether or not this identifier was found is determined. If not found, the process shifts to step 1061 and transfer is prohibited. In step 1053, if the identifier is found, a song is selected in step 1054, and a transfer command is made. Next, in step 1055, the data to be transferred is searched for from the data control table at the transfer source, and the flag is checked in step 1056. If the flag is a “1” in step 1057, then the process shifts to step 1061 and transfer of that data is prohibited since transfer has already occurred. If the flag is a “0”, then the data is transferred instep 1058, and instep 1059 the data control table is rewritten.
The related art had the problem that imparting added (unique) value to information was difficult since information stored on a semiconductor storage medium was easily copied onto another semiconductor storage medium. Stated conversely, in order to prevent information of high added (unique) value from being easily copied this information was not distributed by semiconductor storage mediums.
In a method of the related art to distribute information of high added (unique) value while preventing illegal use by copying, the server 903 encoded the information of high added (unique) value based on the unique ID of the playback equipment 911 so that listening in on the communication system path and illegally using the same information could be prevented.
When passing encoded information from the transfer source device to the transfer destination device, a two-step combination, of “Encoding and transferring unique (added) value information such as music data by means of a common key encoding method.” and “Encoding and sending the common key used for encoding by the public key encoding method.” was generally used on account of the processing speed and simple key management. Since in the latter encoding, an encoding key capable of being decoded at the transfer destination device was utilized (keys were shared), information of significant value could be utilized at the transfer destination device.
In the method of the related art, for transferring information of high added (unique) value without copying the information between storage mediums, the transfer of data could be achieved by data copy permit/prohibit flags, and by installing a function to prohibit data at the data transfer source after copying the data. However, in both of these methods of the related art, the communication path for information between the transfer source and the transfer destination was not adequately protected and information of high added (unique) value could be illegally acquired by intercepting (listening in) information on the same communication path. Further, This procedure has a point when usable data was present at the data transfer source and the data transfer destination, so the data at data transfer source and the data transfer destination were both capable of being utilized due to an interruption in communications between the data transfer source and the transfer destination.